The communication system that is a successor to the Wideband Code Division Multiple Access (WCDMA) system, High-Speed Downlink Packet Access (HSDPA) system, High-Speed Uplink Packet Access (HSUPA) system and the like i.e. Long Term Evolution (LTE) has been determined by 3GPP that is the standardization group of WCDMA. As a radio access scheme in LTE, an Orthogonal Frequency Division Multiplexing Access (OFDMA) system is defined in downlink, while a Single-Carrier Frequency Division Multiple Access (SC-FDMA)) system is defined in uplink.
The OFDMA system is a multicarrier system for dividing a frequency band into a plurality of narrow frequency bands (subcarriers), and assigning data onto each subcarrier to perform transmission. The subcarriers are orthogonal to one another and arranged densely on the frequency axis, high-speed transmission is thereby achieved, and it is expected enhancing spectral efficiency.
The SC-FDMA system is a single-carrier transmission system for dividing the frequency band for each terminal, and performing transmission using frequency bands different from one another among a plurality of terminals. It is possible to reduce interference between terminals with ease and effectively, it is further possible to reduce variations in transmission power, and therefore, this system is preferable from the viewpoints of low power consumption in the terminal, wide coverage, etc.
In addition, various code multiplexing transmission (or spreading transmission using spreading sequences) are applied to LTE (for example, see Non-patent Document 1). For example, on the PHICH (Physical Hybrid-ARQ Indicator Channel) in downlink, code multiplexing is performed using the Walsh code to transmit ACK/NACK of hybrid ARQ in response to the PUSCH (Physical Uplink Shared Channel). Further, on the PUCCH (Physical Uplink Control Channel) in uplink, spreading transmission is performed using CAZAC sequences.